USHistory.org, DigitalHistory.UH.edu, and AmericanYawp.com are sources of free online history books. Each available textbook represents the collaborative efforts of professional, published historians affiliated with such organizations as the American Historical Society and the Independence Hall Association.
As of June 2015, "American History" is a free history textbook available at USHistory.org. The text covers the Pre-Columbian period to the Reagan years. The text of "Digital History," the free online history textbook offered by the University of Houston begins with stories about the first Americans and concludes with events in 2012.
"Digital History" is fully interactive and features the textbook portion, media, supportive documents and teaching resources for each increment of time. "The American Yawp," the American Historical Association's free textbook, consists of two main parts, "before 1877" and "after 1877."